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Abstract

Many variations of conveyor, facility, and trailer
designs are available to aid the human operator in
manual materials handling (MMH). This thesis
describes an investigation to determine which of
four different designs used in trailer MMH place
the least physical stress on the human operator
when unloading materials. Each trailer MMH
design was evaluated by the criteria of
biomechanical loading, working posture,
physiological measure, and subjective rating of
exertion. These four methods were used to
generate four dependent measures: L5/S1
Compression Force, OWAS Action Category,
mean heart rate, and Borg CR-10 RPE.
While no single assessment method provided a
clear means for quantifying level differences in
physical stress among MMH conditions, the
methods employed furnished insight into which
techniques and protocols might be useful in
studying similar working situations. Based on
relative sensitivity, ease of application, and
administrative and equipment costs, the OWAS
method was recommended as an assessment
method useful for evaluating similar MMH work.
The summary results of the four methods
provided information to meet the experimental
goals of this research and allowed conclusions to
be drawn for the major areas of interest.
Specifically, statistically significant differences
were found between the Drop-frame - Floor
Rollers condition and all other conditions in the
SSPM - Placement analysis, between the
Flat-floor - Power and the Drop-frame -
Suspended Rollers conditions in the OWAS -
Acquisition analysis, and between the Drop-frame
- Suspended Rollers and the Drop-frame - Floor
Rollers conditions in the OWAS - Placement
analysis.